Method of extracting lubricating oil fractions



Patented July 15, 1952 James A. Anderson,

ward F. Wadley,

of Delaware 1 This-invention'relates to an improved method ofrefining-lubricating oils. Particularly, it relates to a solventextraction process whereby the organic acid content of lubricating oilsmay be effectively reduced.

Lubricating oil distillates derived from naphthenicand mixed base crudepetroleum oils frequently contain appreciable quantities of naturallyoccurring -organic acids. These organic acids-such as naphthenic acids,even if present in alubricating oil in relatively small concentrations,are corrosive to engine parts at the high temperatures-to which suchoilis usually subjected. It is-important, therefore, that motor lubricantsnot only have satisfactory viscosity index, color, pour and stabilitycharacteristics, but also contain organic acids in concentrationsinsufilcient to cause corrosion difiiculties under severe temperatureconditions.

Inpresent commercial practice, it is customary to improve the viscosityindex characteristics, of untreated lubricating oil distillates bytreatment in, theliquid phase with a solvent that has a preferentialselectivity dex naphthenicand aromatic-type (relatively lessparafiinic-type) compounds as compared with-the-high viscosity index(relatively more parafiinic-type) compounds. Phenol, furiural, aniline,nitrobenzene and the like are typical solvents used for this purpose.Solvents, such as phenol, that do not react with organic acids alsodemonstrate a preferential selectivity for organic acids of the typeusually found in lubricating oil distillates derived from naphthenic ormixed base crudes. In a solvent treating process, therefore, the organicacids tend to be separated from the paraflinic constituents. It has beenobserved, however,.that lubricating oil distillates containing?relativelyhigh,concentrations of. organic acids maybe treated with aselective solvent to produce a finished lubricating oil havingsatisfactoryviscosity index characteristics and yet reta "Qsuflicientorganic acids to render the solvent treated oil corrosive to engineparts.

Experience has shown that motor lubricants derived from mixed base andnaphthenic crudes should contain organic acids in amounts below, i. e;having a neutralization value below, an equivalent of 0.1 milligram KOHper gram of. oil to render said lubricant non-corrosive to engine parts.Experience also has shown that the liquid phase extraction of lubricantdistillates containing organic acids in amounts below an equivonemilligram KQH per gram of said alent of distillate with a solvent, suchas phenol, genera ,for the low-viscosity ining equipment isnon-corrosive amounts of organic acids.

fUNl-TED, Y STATES P EIN l I METHOD OF EXTRACTING LUBBICATING OILFRACTIONS J1'., Clyde MJFloyd, and Ed- Baytown, Tex.,'assignors, by.mesne ass'ignments,;to Standard Oil Develop- I ment Company, Elizabeth,N. J.,

a corporation ally produces high yields of a finished lubricant having ahigh viscosity index and containing been found, for example, thatlubricant distillates containing organic acids in amounts substantially.above an equivalent of one milligram. KOH per gram of said distillaterequire solvent extracting to a lower yield of finished lubricant havinga higher viscosity .index than is normally required inorder to reducethe organic acid content of said lubricant to non-corrosive amounts.Sucha motor lubricant is said to be over. ex-, tracted; that is, onerequirement imposed on, the finished lubricant is met at the expense ofother requirements imposed thereon.

In order to effect a substantially complete .re-. moval of the organicacids from the high viscosity index paraflinic constituents, it isfrequently necessary to increase the severity of the solvent treat, thatis, increase the ratio of solvent to lubricating oil, above the normalrequired to produce an oil of desired viscosity index. Increasing thesolvent treat decreases the. yield of finished lubricating oilobtainedin the. treating process. In addition, if the solvent treat-'operated at its maximum ca-. pacity, an incr'ease in solvent treat abovenor; mal: necessitates decreasing the; amount of oil feed whichmaybeintroduced. Increasing the severity of the solvent treat also isdisadvan-r tageous in that natural inhibitors present in certain typesof lubricating" oil distillates and known to be beneficial to motorlubricants are remove from. the finished lubricant.

An alternative method 0 acid content of motor lubricants is that oftreating a topped crude or lubricating 'oil distillate with an alkalinematerial. For example, it is well known to the 'art to remove organicacid-s present in'petroleum oil fractions by distilling" a materialsremaining in the residue is relatively high, the residue. may beunsatisfactory for asphalt manufacture or for use as a fuel oil.

In U. S, 2,451,025, issued October 12, 1948,11) Harold L. Ellendenamethod is described for removing organic acids from lubricating oildistillates in a process involving treating a lubricating oil distillateduring distillation thereof with an'alkaline reagent, such as sodiumhydrox lde,.followingwhich a fraction; boiling in the It hasf reducingthe organic tion. This process is quite effective and allows theobtaining of a solvent rafiinate having the desired characteristicswithout requiring the lubricatingoil to be overextracted in the solventextraction step to produce a product having the requisite low,neutralization value. It smite seen, however, that the aforesaidEllenderpatent requires the addition of an alkaline reagentto thedistillation Zone in which the .mineral' Oi].

lubricating fraction is being segregated from a.

topped crude petroleum. Thus, under some conditions the presence of thealkaline reagent in the distillation tower may be harmful, especiallywhen long contact times are employed and excessive amounts of thealkaline reagent are necessary since the. presence of alkaline reagents,such as sodium hydroxide, may affect. deleteriously the ferrous metalsemployed in distillation towers. Itis well'known that sodium hydroxidemay cause caustic embrittlement of'ferrous metals when incontact'therewith at high temperatures.

gIt is, therefore; the mainobject of the present invention to provide animproved process for refining mineral lubricating oils.

Another object of our invention is 'to provide an economical processwherein maximum, yields ofs'olvent extracted lubricating oils, meetingboth viscosity index and organic acid contentrequirement's,may beproduced from suitable mineral oils.

A still further object of our invention is to provide a selectivesolvent extraction process in which maximum quantities of oil andminimum quantities of solvent are circulated to produce lubricating oilof desired high viscosity index and low organic acid contentwithoutoverextracting the oils. v V I Still othe r objeots .and advantageswillbe apparent to workers-skilled in the artgto which thepresent'invention relates. I In accordance with the-present invention,it has now been found that'lubricating-oil=fractions1ob tained fromcrude petr'oleums and m'ineral oil distillates may be "solvent extractedto obtain a solvent raffinate having thegrequired low neutrali'zationvalue without overextracting the oil.

,Thus, for example, in-accordanoewith the present invention, alubricating oilfraction, such as a mineral'oil distillateboiling in the"lubricating oil boiling range and having'lubricating oil co nponentstherein is subjected to extraction with phenol, such as anhydrous oraqueous phenol, containingfa small but. effective amount of an alkalimetal phenolate which may bejformed in situ' by adding an alkali metalhydroxide to the phenol, under conditions to form an extract phase and araffinate phase which are recovered separately. The reffinate phase,from which the undesirable components have 'been removed in the phenol,is subjectedtoia stripping operation-in' which the residualphenol isremoved therefrom to allow recovery of the desirable motoroil'fractionswhich, by virtue'of the pres-f ence of the alkali metal hydroxide orphenolate during the extraction operation in the presence of phenol,allows the obtaining of a motor oil having the required lowneutralization value.

7 Alternatively, dependi-ngcn the characteristics to the phenol priortocontact with the oil being extracted or to the solvent rafilnatecontaining the phenol. Addition of the alkali metal hydroxide converts asmall amount of the phenol to the corresponding phenolate which; it isbelieved, by reaction with-the organic acids releases the alkali metalhydroxide which serves to neutralize the organic acids.

-Therefore,; it is within the purview of our inyen'tion to add alkalimetal phenolates rather,

than alkali metal hydroxide to the phenol.

Therefore, the invention may be described briefly as involvingmaintaining alkali metal phenolate tro duced by line-|3 givenin moredetail hereinafter.

" of the oil and therefore, the 'treating operations to;whichthe oilmaybe subsequently subjected, the ;alkali metal hydroxide may be'addedeither in the phenol solvent and solvent extracting the lubricatingoiliraction with the mixture ofa1- kali metal phenolate and phenol undercondi! tions to form a raffinate phase and an extract phase, the twophases being separately recovered and processed for recovery of phenoland the hydrocarbons containedin the two phases.

In the foregoing briefdescription, it ;is seen that the essence of thepresent 'invention'resides in providing a process 'inwhich -alubricating-oilfraction, such as a mineral oil -distillate,is sub jectedto contact with phenol containing semen amount of an alkali metalphenolate -which'- n lay beformed in situ by adding to the phenol-asmall buteffective amountof an =alkali=metal hydroxide. The presence ofalkali metal phenolate in a small but effective amountiin the phenolcauses the removal of the organic-acids and allows the obtaining of a'soIVentraffinate having a neutralization value no greater -than 0. 1milligram. KOH per gramwof oil without overextraction of the oil. [Asmentioned befor'e,-'an alternative mode of thepresent invention involvsadding the alkali metal phenolateto the solvent rafilnate containingphenol or forming the alkali metal phenolate-in the solvent-rafiinatecontaining phenol to obtain amotor oil fraction having the-desired loworganicacid content.

The invention will be better understood'by' contacting equipment such asbell captrays, pack ing, and the like to allow intimate contact between. the mineral oil distillate boiling inthe lubricatingpil boilingrange and having lubri eating oil qualities which is introduced intozone H by line l2 and flows upwardly therein contacting the down-flowingphenol which is introduced into zone Ii byline 13. The phenol in-j maybe sub amanyam hydrous phenolyxtl'iatia it may havefaph'enol content ofapproximately 100% for Zitf may be aqueous phenol containing -approXilfrlalily 10%? of water. Thus, itis understood thatfphen'ol containingto phenoLmay .bejintro-l duced byline I 3 and,employedas a sollv'ent "nsolvent extraction zone Ii. Conditionsare ad?- justedin extractionzonefLil to produce a-Ifaf finate phase and ,an extract phase... ,"Suchcondi-tions'are well'knownto the art, but-will :be

4 The phenol, prior to introduction into .zone' I l has addedtoit byline 14 controlled by valve 15 a small but eiiective amount ofsodium-hydroxide which is withdrawn from tank le'b pump 1". The amountof sodium hydroxidet'in troduced into the'phenol to cause the formationKor per gram'of oill Usually,

o'iLff In. any valuegoi above about l'.0 milligramKO'I-Il per be themore aromatic and .ftheextent to which it isdesired toremovej'suchacids. The mineralmotor'oifdistillate may have n organicflacidfcontentcorresponding to 'aJneutralization value of approximately3.5"mi'lligrams on however, the neutralization value will be somewhatlower and "mayb about 2 milligramsKQI-I per gram of event, oil'ha'ving'a neutralization grain] of; oil is generally 'too' high to allow theproduction of a ra'fiinate having the desired neutralization valueno'greater than aboutO-J milligram KOI-I per; gram of oil'withoutoverextract- 'ing hydroxide or sodium phenolate" introduce'dporcontained in the 'phenol'should usually at' least be the theoreticalamount required to allow the Obtaining of a solvent rafilnate having aneutralization value of no greater than about 0.1 milligram KOH per gramof oil. In cases where it is not necessary to obtain extracted oilshaving such low neutralization values or in the event the oil to beextracted has a low neutralization value, such as below 1.0, andrequires a light solvent treat, it may not benecessary to maintain thealkali metal hydroxide or phenolate content of the solvent at thetheoretical amount. Generally, the amount of alkali metal phenolatemaintained in the solvent should, on a; molar basis, be equivalent tofrom 0.2 to 3.0 times the theoretical amount of KOH required "toneutralize acidic bodies in the oil to be "extracted.

As mentioned before, the' phenol containing the sodium phenolateeitheradded thereto or produced in situ contacts countercurrently' theascending mineral motor oil distillate in extraction zone I] and byadjustment of conditions therein, causes the formation of raffmate andextract phases. The extract phase is withdrawn from zone II by line l8and is discharged thereby into a stripping zone l9 which is providedwith a heating means 20 which is illustrated by an internal coil whichwill be understood to embody any of the well known types of heatingmeans available to the industry. Stripping zone I9 is provided withinternal baffiing equipment to allow separation of the phenol from thehydrocarbon constituents contained therein which will naphthenicconstituents as opposed to the more paraffinic constituents which willbe found in the solvent raffinate, The phenol is removed from strippingzone [9 by line 2| for reuse in the process while the predominantlyaromatic and naphthenic constituents removed from the mineral motor oildistillate as a solvent extract are discharged from stripping zone l9 byline 33 to be used as a cracking stock or in other uses as may bedesired.

A solvent raffinate is removed from extraction zone II by line 22 and isdischarged thereby into a stripping zone 23 which is similar tostripping zone I9 and is provided with a heating means illustrated :bycoil 24 which may be any of the well known heating means available tothe industry. Zone 23 is provided, like zone IS, with internal,contacting equipment to allow separation between the phenol and thepredominantly paraffinic constituents found in the Conditions areadjusted in while solvent raflinate. stripper 23 to remove phenol byline 25 the oil. Therefore, the amount "of'sodium' be conne d; to; n 11pi mp l and tank nd.albwinetheso y h fi introduction of sodium ,droxideto line 22, it, may be-desirable toyco'nthe desired motor 'oilcomponents are removed from zone 23 by line 26. we

When sodium hydroxide or sodium phenolate is not. added to thephepqrhalternatiyely it [may be added to thesolvent raffinate inline22 5When this is desired, valve 'I S-in line M-is closed and va ve 21;:11 li'28. is enema. low l e '28 o troduced into the solvent raffinatecontaining phenolto cause formation in situroi sodium phenolate andallowthe obtaining. of arirafflnate having an organicacidcontentcorresponding to a neutralization value no greater than 0.l milligramKO-H per grarnof oil. When thelatter 1 operation is; employed, it willbe understood v that I a suitable incorporation means, not shown, willbe provided in line 22to allow intimat' admixture of the solventrafiinate with" Ithej sodium hydroxide or sodium phenolateintroduced'thereto by line 28.

When the sodium ,phenolatesare .formedb'y phenolate or sodium hyftactthe phenol-free oil, which may contain smallquantities of sodiumphenolate's, with clay.

Therefore, a clay contacting zone. 29 is'provided wherein the oilcontaining small quantities of sodium phenolate 'may be contacted at'arela- 'tively high temperaturesuch as in tlierangeof 350 to'450? F.with' afsiiitable contactlclay'such as illustrated by acid'treatednatural clays or bentonite, and the like," When this operation isconducted valve 3i l'.'in line 26 will be opened, valve 3| in line 32will'be'closed, and1valve33 jinline 34 will be, opened, allowing the oilto'be routed byline zfiltdclaycontacter zawhere it is intimately admixedwithv cIay Which is subsequently removed from the oil by m'eans noltshown;

zone 29 by line 34"into line 32, cooled in cooler 35 in line 32, anddischarged thereby tosuitable storage facilities, not shown, fromwhencethe oil may be withdrawn for use as a commercial lubricating oilhaving 'a neutralization 'valuejfno 'greate'rthan; one milligram KOH pergramlof oil. s. V

When 1 the sodium hydroxidev or sodium phenolate is introduced intothephenol byline [4 connecting into line l3, the employment of claycontacting zone 29 may be dispensed with andthe oil may bypass thiszonefbyi lclosing valve 30 in line 26 and valve 33 in linev34. Withvalve3| in line 32 in the open position, the motor oil substantially free ofphenol is routed 'by'line 2'6 and line 32 through cooler 35 to storagefor use .as a commercial motor oil having the desired low neutralizationvalue as mentioned before.

Although the inventionhas been described andillustrated above withrespect to tank 6 containing sodium hydroxide, it will be apparent thatthis tank maycontain alkali metal hydroxide such as sodium hydroxide oran alkali metal phenolate. Thus, provision is made by line 1, controlledby valve 8, to introduce alkali metal hydroxide to tank 16 and provisionis also made to introduce alkali metal phenolate thereto by line 9,controlled by valve In.

While the invention has been described and illustrated with respect toemployment of sodium phenolate or sodium hydroxide, it is to beunderstood that the phenolates or hydroxides oi the other alkali metals,such as lithium and potassium phenolates or hydroxides, may be employedin lieu of sodium hydroxide or sodium and the clay-treated oildischarged" from encased phenolate, =but that the latter are ito'bepreferred by virtue of their ability? r r a V In thepresentinvention itwill be obvious to those skilled in the art that 'the critical quantityo'f-alk ali metal hydroxide or alkali metal-phenolate introducedinto thesolvent extraction sysoheapness and avail- :tem will depend onthe'concentration of organic acids contained-in the lubricating oilfractions subjected'to the process of the present invention. The organicacidcontent of the lubricating oil distillate must be reduced'sufiiciently to permit obtaining the highest possible yield of solventextracted lubricating oil meeting viscosity index and acid contentrequirements.- On the other hand; the quantity'of alkali metal hydroxideor alkalimetal phenolate introduced into the extraction system should besufiicient to react with the" organic acid content of the motor oilfraction without providing such an excess amount that the phenol will bereacted with and cause loss of the valuable solvent. In general, it ispreferred to employ an amount of alkali metal hydroxide orpheno late ineither the solvent or 'rafilnate phase that is about theoreticallyequivalent to the amount of KOH required to neutralize acidsjin eitherthe oil charge or remaining in the flraifinate'phase; however, on amolar basis, as ilittleas 0.2 mol alkaline material per mol of KOH(determined from theneutralization value) may be used wherethe treatingconditions are such that the phenol solvent issufficiently selectiveto'removemo'st of the acids. '"On the other hand, as" much as 3 molsalkaline material per mol of KOH .required to jneutralize the acids maybe used under extreme conditions 'where substantially complete removalof th'e organic acids from the .oil is desired and where the acids aredifii cult to extract. s 'Ihe conditions employed in the solventextraction zone I l mayvary with the composition of the feedstockcharged. Inthe case of treating Ewample' II solvent used in theextraction step andthegneu- Example I.

traliz'a'tion value 01. the oil charge, is equivalent on a molar basisto 1.1 times the theoretical amount 7 of KOH required to neutralizeorganic acidsinthe oil treated. The tower temperature conditions werethe same as those employed in The yield of solvent rafiinate in thisoperation was 56% by volume of the motor oil charged and had a viscosityindex of 61. The

neutralization value of raffinate was 0.059 milligram KOH per gram ofoil, which is well below the specification requirementin this particularcase.

Ezzzample III In this particular operation; the same ratio of Oil tosolvent and the same temperature conditions were used in the treatingstep thatwere used in Example II. A 56% yield of rafflnate having aviscosity index of "61 was obtainedgjIn this operation, howeverjsodiumhydroxide was notadded to theanhydrous'plhenol prior ,to theextractionstep, and the neutralization value of the .rafiinate was 0.308milligram-KOH per gram of oil, which isgreatly in excess of thespecification figure and of the neutralization value of the raifinateproduced in Example II.

It will be observed fromthe foregoingexamples that thepresent' inventionallows vastly improved distillates derived from coastal crudes, oil tosolvent ratios inthe range from 120.5 to about 1 :3.0, treatingtemperatures in the" range from about to 250 F., and essentiallyatmospheric pressures are generally satisfactory. As mentioned before,the phenol may be'substantially anhy+ 'drous or may contain up to about10% by volume of water. i

In order to demonstrate the invention further, the following examplesare given whichshould notbe construed as limiting the invention inanymanner.

' Example I A motor oil distillate having a Saybolt Universal viscosityof approximately-950 seconds at 100 F., a viscosity index of 24, and aneutralization value of 1.25 milligrams KOH per gram of.

oil was extracted-with 100% phenol using an "oil tosolvent ratio of1:15; The extraction was carried out in a towerhaving 'five theoreticalstages'with a top tower temperature of F. and a bottom temperature of100 F. 1 5.43% 'yield, based onthe charge, of raflinate having aviscosity index of 68 and a neutralization value of 0.085 milligram KOHper gram of oil was'produced during the extraction operation. Inthisparticularoperation it was desired to produce a solvent rafiinatemeeting a viscosity index specification of 60 and a neutralization valuespecification df-less-than 0.1 milligram KOH per gram 1 of'oil, but itwas necessary to overextract the oil tomeet the'neutrali'zation valuespecification.

results both in yield and quality of finished product without resorting'to' overextraction thereof.

It isfurther noted that the-invention permits employing much lowersolvent treats than are conventionally permitted to obtain a producthaving a lowneutralization value by employinga small amount of sodiumhydroxide or sodium phenolate in the solvent instead of a relativelylarge amount of solvent to remove acidic bodies'from the oil;

It should be mentioned that anhydrous phenol was employed in theforegoing examples, and, therefore, the yields of finished rafiinatewere somewhat lower than would be obtained-byusing aqueous phenol. Forexample, a distillate similar to that used in the Examples but having a1.5 neutralization value may be treated at a temperature of F. with amixture comprising 96% phenol and water (oil to solvent ratio of '1 :15)to obtain a 63% yield of r-afiinate having a viscosity index of 68 and aneutralization value of 0.08 milligram KOH per gram of oil. By adding asmall amount ofan alkali-metal hydroxide tas neutralization valuespecifications. Since anhydrous phenol is somewhat more selective toacidic bodies in the oilthan is the aqueous phenol, it'is generallynecessary to use a slightly higher amount of alkali metal hydroxide orphenolate based on the acidic bodies and/or a higher solvent treat whenusing the latter material as com- ;pared to the anhydrous phenol.

It is, therefore, seen that by practicing the present invention, it ispossible to remove acidic bodies from lubricating oil distillates by amodified solvent which comprises phenol and a'small amount of an alkalimetal hydroxide or phenolate which has a greatly improved selectivityfor the acidic constituents. It is possible to obtain an extracted oilmeeting both neutralization value and viscosity index requirementswithout resorting to overextraction which causes the loss of valuablelubricating oil constituents. Such high viscosity index constituentswhere overextraction occurs are lost in the solvent extract and,therefore, are degraded to cracking stocks whereas in the practice ofthe present invention, these valuable constituents may be used aslubricating oil components.

The nature and objects ofthe present inven' tion having been completelydescribed and illus trated, what wewish to claim as new and useful andto secure by Letters Patent is:

1. A method for solvent extracting a mineral lubricating oil distillatefraction which contains small quantities of naturally occurringnaphthenic acids, has a neutralization value in the range from about 1to about 3.5 milligrams KOH per gram of oil and would be over extractedif extracted with phenol alone in such an amount as to reduce its acidneutralization value below .1 milligram KOH per gram of oil, whichcomprises the steps of intimately contacting said fraction with a phenolsolvent containing no more than 10% water and a small but effectiveamount of an alkali metal phenolate equivalent to from 0.2 to 3.0 timesthe theoretical amount of KOH required to neutralize acidic bodies insaid fraction under conditions including a temperature in the rangebetween 100 and 250 F. and substantially atmospheric pressure to form arafiinate phase and an extract phase andseparately recovering saidphases. 1

2. A method in accordance with claim 1 in which the phenolate is formedin situ by adding to said phenol solvent an alkali metal hydroxide in anamount in the range from .2 to 3.0 times the theoretical amount of KOHrequired to neutralize acidic bodies in said fraction.

3. A method in accordance with claim which the alkali metal is sodium.

4. A method in accordance with claim 1 in which the alkali metal ispotassium.

5. A method in accordance with claim 1 in which the alkali metal islithium.

6. A method for solvent extracting amineral lubricating oil distillatefraction which contains small quantities of naturally occurringnaphthenic acids, has a neutralization value in the range from about 1to about 3.5 milligrams KOI-I per gram of oil and would be overextracted if extracted with phenol alone in such an amount as to reduceits acid neutralization value below .1 milligram KOH per gram of oil,which comprises the steps of forming a first stream of said lubricatingoil fraction, forming a second stream of phenol containing no more thanwater, adding to said second stream an amount of an alkali metalhydroxide equivalent to from 0.2 to 3.0 times the theoretical amount ofKOH required lin to neutralize acidic bodies in said oil, contactingsaid first stream with said second stream under conditions including atemperature in the range from about to 250 F. and substantiallyatmospheric pressure to form a raffinate phase and an extract phase,separating said phases, separately removing phenol from said separatedphases, and recovering from said rafiinate phase a motor oil fractionhaving a neutralization value less than 0.1 milligram of KOI-I per gramof oil.

7. A method for solvent extracting a mineral lubricating oil distillatefraction which contains small quantities of naturally occurringnaphthenic acids, has a neutralization value in the range from about 1to about 3.5 milligrams KOH per gram of oil and would be over extractedif extracted with phenol alone in such an amount as to reduce its acidneutralization value below .1 milligram KOH. per gram of oil, whichcomprises the steps of contacting said distillate with phenol solventcontaining no more than 10% Water under conditions including atemperature in the range between 100 and 200 F. and substantiallyatmospheric pressure to form a rafiinate phase and an extract phase,separating said phases,

maintaining in said rafi'mate phase a small but effective amount of analkali metal phenolate equivalent to from 0.2 to 3.0 times thetheoretical amount of KOI-I required to neutralize acidic bodies in saidfraction, separating phenol from said raffinate phase, and recoveringfrom said raffinate phase a lubricating oil fraction substantially freeof said acidic bodies.

8. A method in accordance with claim 7 in which said lubricating oilfraction substantially free of said acidic bodies is treated to removesodium phenolate therefrom.

9. A method in accordance withclaim 7 in which said phenolateis formedin situ by adding to said solvent raffinate an alkali metal hydroxide inan amount equivalent to from 0.2 to 3.0-times the theoretical amount ofKOH required to neutralize acidic bodies in said rafiinate phase toobtain a motor oil having a neutralization value less than 0.1 milligramKOI-I per gram of oil.

10. A method in accordance with claim 'I in which the alkali metal issodium.

11. A method in accordance with claim '7 in which the alkali metal ispotassium.

12. A method in accordance with claim 7 in which the alkali metal islithium.

JAMES A. ANDERSON, JR. CLYDE M. FLOYD. EDWARD F. WADLEY.

REFERENCES CITED The following references are of; record in the fileofthis patent:

UNITED STATES PATENTS

1. A METHOD FOR SOLVENT EXTRACTING A MINERAL LUBRICATING OIL DISTILLATEFRACTION WHICH CONTAINS SMALL QUANTITIES OF NATURALLY OCCURRINGNAPHTHENIC ACIDS, HAS A NEUTRALIZATION VALUE IN THE RANGE FROM ABOUT 1TO ABOUT 3.5 MILLIGRAMS KOH PER GRAM OF OIL AND WOULD BE OVER EXTRACTEDIF EXTRACTED WITH PHENOL ALONE IN SUCH AN AMOUNT AS TTO REDUCE ITS ACIDNEUTRALIZATION VALUE BELOW
 1. MILLIGRAM KOH PER GRAM OF OIL, WHICHCOMPRISES THE STEPS OF INTIMATELY CONTACTING SAID FRACTION WITH A PHENOLSOLVENT CONTAINING NO MORE THAN 10% WATER AND A SMALL BUT EFFECTIVEAMOUNT OF AN ALKALI METAL PHENOLATE EQUIVALENT TO FORM 0.2 TO 3.0 TIMESTHE THEORETICAL AMOUNT OF KOH REQUIRED TO NEUTRALIZE ACIDIC BODIES INSAID FRACTION UNDER CONDITIONS INCLUDING A TEMPERATURE IN THE RANGEBETWEEN 100* AND 250* F. AND SUBSTANTIALLY